The broad, long-term objective of this project is the advancement of MRI as a tool for vascular diagnosis. The specific goal is to improve a method of MRI known as phase-contrast MR angiography (PC-MRA) with several novel contributions that make it more practical to use for both clinical diagnosis and basic science research, and that improve the accuracy and breadth of information obtained from this method. PC-MRA has a unique potential among all imaging modalities to yield reproducible, quantitative four-dimensional (space + time in the cardiac cycle) information about blood flow velocities and patterns. This information has potential in assessing vascular morphology in a clinical setting, understanding the hemodynamics that may contribute to pathogenic processes, predicting the risk of atherosclerosis and of acute events such as stroke and aneurysm rupture, and aiding in the design of vascular grafts and methods of graft placement. Despite its potential, PC-MRA is not routinely used currently, in part because of long imaging times and its inability to accurately characterize disordered flow. Work proposed in this application will attempt to advance PC-MRA in four key areas of development: 1. A simple, robust method of estimating wall shear stress and flow disorder from PC-MRA data will aid in quantification of wall shear stress, and aid in visualization of areas with flow disorder. 2. A rapid method for data acquisition will be developed and implemented. This, along with new methods for data reconstruction, will add flexibility to data collection and reduce artifact. 3. Expansion of a previously proposed technique will increase greatly increase data SNR, subsequently improving vessel conspicuity as well as the precision of flow velocity measurements. 4. Data processing will improve the accuracy and information content of the reconstructed images.